Wild yam (Dioscorea villosa)
Natural Standard Bottom Line Monograph, Copyright © 2013 (www.naturalstandard.com). Commercial distribution prohibited. This monograph is intended for informational purposes only, and should not be interpreted as specific medical advice. You should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.
While some complementary and alternative techniques have been studied scientifically, high-quality data regarding safety, effectiveness, and mechanism of action are limited or controversial for most therapies. Whenever possible, it is recommended that practitioners be licensed by a recognized professional organization that adheres to clearly published standards. In addition, before starting a new technique or engaging a practitioner, it is recommended that patients speak with their primary healthcare provider(s). Potential benefits, risks (including financial costs), and alternatives should be carefully considered. The below monograph is designed to provide historical background and an overview of clinically-oriented research, and neither advocates for or against the use of a particular therapy.
Atlantic yam, barbasco, batata silvestre, black yam, China root, colic root, devil's bones, Dioscorea, Dioscorea barbasco, Dioscorea hypoglauca, Dioscorea macrostachya, Dioscorea opposita, Dioscorea villosa, Dioscoreae (family), diosgenin, Mexican yam, natural DHEA, phytoestrogen, potassium, rheumatism root, shan yao, white yam, wild yam root, yam, yellow yam, yuma.
Note: "Yams" sold in the supermarket are members of the sweet potato family and are not true yams.
It has been hypothesized that wild yam (Dioscorea villosa and other Dioscorea species) possesses dehydroepiandrosterone (DHEA)-like properties and acts as a precursor to human sex hormones such as estrogen and progesterone. Based on this proposed mechanism, extracts of the plant have been used to treat painful menstruation, hot flashes, and headaches associated with menopause. However, these uses are based on a misconception that wild yam contains hormones or hormonal precursors - largely due to the historical fact that progesterone, androgens, and cortisone were chemically manufactured from Mexican wild yam in the 1960s. It is unlikely that this chemical conversion to progesterone occurs in the human body. The hormonal activity of some topical wild yam preparations has been attributed to adulteration with synthetic progesterone by manufacturers, although there is limited evidence in this area.
The effects of the wild yam saponin constituent "diosgenin" on lipid metabolism are well documented in animal models and are possibly due to impaired intestinal cholesterol absorption. However, its purported hypocholesterolemic effect in humans and the feasibility of long-term use warrant further investigation.
There are few reported contraindications to the use of wild yam in adults. However, there are no reliable safety or toxicity studies during pregnancy, lactation, or childhood.
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Animal studies have shown that wild yam can reduce the absorption of cholesterol from the gut. Early studies in humans have shown changes in the levels of certain sub-types of cholesterol, including decreases in low-density lipoprotein (LDL, or "bad cholesterol") and triglycerides and increases in high-density lipoprotein (HDL, or "good cholesterol"). However, no changes in the total amount of blood cholesterol have been found. More studies are needed in this area.
Most studies have not shown a benefit from wild yam given by mouth or used as a vaginal cream in reducing menopausal symptoms. However, replacing two thirds of staple food with yam for 30 days was shown to improve the status of sex hormones, lipids, and antioxidants in a recent study in postmenopausal women. The authors suggest that these effects might reduce the risk of breast cancer and cardiovascular diseases in postmenopausal women. Further research is needed before a recommendation can be made.
Hormonal properties (to mimic estrogen, progesterone, or DHEA)
Despite popular belief, no natural progestins, estrogens, or other reproductive hormones are found in wild yam. Its active ingredient, diosgenin, is not converted to hormones in the human body. Artificial progesterone has been added to some wild yam products. The belief that there are hormones in wild yam may be due to the historical fact that progesterone, androgens, and cortisone were chemically manufactured from Mexican wild yam in the 1960s.
*Key to grades:A: Strong scientific evidence for this use; B: Good scientific evidence for this use; C: Unclear scientific evidence for this use; D: Fair scientific evidence against this use (it may not work); F: Strong scientific evidence against this use (it likely does not work).
The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious and should be evaluated by a qualified health care professional.
Antifungal, anti-inflammatory, antiviral, asthma, bile flow improvement, biliary colic, breast cancer, breast enlargement, cancer prevention, cardiovascular disease, carminative (prevents gas), childbirth, cramps, croup, decreased perspiration, diverticulitis, energy improvement, excessive perspiration, expectorant, intestinal spasm, irritable bowel syndrome, joint pain, libido, liver protection, low blood sugar, menstrual pain or irregularities, morning sickness, nerve pain, osteoporosis, pancreatic enzyme inhibitor, pelvic cramps, postmenopausal vaginal dryness, premenstrual syndrome (PMS), rash, rheumatic pain, spasms, urinary tract disorders, uterus contraction, vomiting.
The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.
Adults (18 years and older)
There are no proven effective medicinal doses for wild yam.
Children (younger than 18 years)
Not enough evidence is available to recommend use in children.
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.
Rubbing the skin with Dioscorea batatas (a yam species related to Dioscorea villosa) has been reported to cause allergic rash. Workers exposed to Dioscorea batatas in large amounts and for a prolonged time have developed asthma that is made worse by exposure to the yam. A person who is known to have an allergy to Dioscorea batatas may also be allergic to other Dioscorea types.
Side Effects and Warnings
Rubbing the skin with Dioscorea batatas, a related yam species, has been reported to cause a rash at the site of contact. Wild yam cream caused no rash in 23 healthy women in one reported study. In another study, wild yam given by mouth was reported to cause stomach upset at high doses.
Wild yam was believed in the past to have properties similar to the reproductive hormone progesterone, but this has not been supported by scientific studies. It has been suggested that some wild yam creams might be tainted with artificial progesterone. Based on theoretical hormonal properties and possible progesterone contamination, people with hormone-sensitive conditions should use wild yam products with caution. This caution applies to people who have had blood clots or strokes and to women who take hormone replacement therapy or birth control pills. In addition, women with fibroids, endometriosis, or cancer of the breast, uterus, or ovary should be aware that these are hormone-sensitive conditions that may be affected by agents with hormonal properties.
Caution is advised in patients with diabetes or low blood sugar and in those taking drugs, herbs, or supplements that affect blood sugar. Blood sugar levels may need to be monitored by a healthcare provider and medication adjustments may be necessary.
Pregnancy and Breastfeeding
Use of wild yam is not recommended during pregnancy or breastfeeding due to a lack of safety information. Wild yam is believed to cause uterine contractions and therefore use is discouraged during pregnancy. Wild yam was once thought to have effects similar to those of reproductive hormones, although this has not been proven in scientific studies. Artificial progesterone may be added to some products.
Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.
Interactions with Drugs
It is not clear whether blood sugar is lowered by Dioscorea villosa (wild yam). Dioscoretine, a compound found in the related species Dioscorea dumentorum (bitter or African yam), has been shown to lower blood sugar levels, but this has not been shown for Dioscorea villosa. Effects on blood sugar in humans have not been reported. Nonetheless, caution is advised when using medications that may also lower blood sugar. People taking diabetes drugs by mouth or insulin should be monitored closely by a qualified healthcare provider. Medication adjustments may be necessary.
Early evidence suggests that wild yam lowers blood levels of indomethacin, a non-steroidal anti-inflammatory drug, and reduces irritation of the intestine caused by indomethacin. Human studies have not been reported in this area and it is not clear if wild yam affects the blood levels of other anti-inflammatory drugs such as ibuprofen (Advil®, Motrin®).
Diosgenin, thought to be the active substance in wild yam, has been found in animals to reduce absorption of cholesterol from the intestine and to lower total cholesterol levels in the blood. Studies in humans show no change in the total amount of cholesterol in the blood, although the amounts of specific types of cholesterol in the blood may be changed; low-density lipoprotein (LDL, or "bad cholesterol") and triglycerides may be lowered and high-density lipoprotein (HDL, or "good cholesterol") may be increased. It is thought that wild yam may enhance the effects of other cholesterol-lowering medications, including fibric acid derivatives such as clofibrate (Questran®), gemfibrozil (Lopid®), and fenofibrate (Tricor®). In animals, wild yam has been found to improve the effect of clofibrate in lowering cholesterol levels.
Tinctures of wild yam may contain high amounts of alcohol and may lead to vomiting if taken with disulfiram (Antabuse®) or metronidazole (Flagyl®).
An early study suggests that wild yam may interfere with the body's ability to control levels of the reproductive hormone progesterone. Progesterone is a key ingredient in some hormone replacement and birth control pills. There are reports that some wild yam products may be tainted with artificial progesterone. Women taking birth control pills or hormone replacement therapy should speak with a licensed healthcare provider before taking wild yam.
Wild yam may also interact with steroids, although human evidence is lacking.
Interactions with Herbs and Dietary Supplements
It is not clear whether Dioscorea villosa (wild yam) lowers blood sugar levels. Although dioscoretine, produced by the related species Dioscorea dumentorum (bitter or African yam), has been shown to lower blood sugar, this reaction has not been seen with Dioscorea villosa and has not been reported in humans. Nonetheless, caution is advised when using herbs or supplements that may also lower blood glucose. Blood glucose levels may require monitoring and doses may need adjustment.
Diosgenin, thought to be the active substance in wild yam, has been found in animals to reduce absorption of cholesterol from the intestine and to lower total cholesterol levels in the blood. Studies in humans show no change in the total amount of cholesterol in the blood, although the amounts of specific types of cholesterol in the blood may be changed; low-density lipoprotein (LDL, or "bad cholesterol") and triglycerides may be lowered and high-density lipoprotein (HDL, or "good cholesterol") appears to be increased.
In an early study, a wild yam preparation was reported to block the body's natural production of progesterone. However, this finding was not supported by later research. There have been several reports that some wild yam products are tainted with synthetic progesterone. Because wild yam may contain progesterone-like chemicals, the effects of other agents believed to have hormone-like properties, in particular those with estrogen-like properties, may be altered.
Wild yam may also interact with potassium vitamin C or steroids, although human evidence is lacking.
This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.
Araghiniknam M, Chung S, Nelson-White T, et al. Antioxidant activity of Dioscorea and dehydroepiandrosterone (DHEA) in older humans. Life Sciences 1996;59:L147-L157.
Hudson t, Standish L, Breed C, et al. Clinical and endocrinological effects of a menopausal botanical formula. Journal of Naturopathic Medicine 1997;7:73-77.
Komesaroff PA, Black CV, Cable V, et al. Effects of wild yam extract on menopausal symptoms, lipids and sex hormones in healthy menopausal women. Climacteric 2001;4(2):144-150. View Abstract
Kubo Y, Nonaka S, Yoshida H. Allergic contact dermatitis from Dioscorea batatas Decaisne. Contact Dermatitis 1988;18(2):111-112. View Abstract
Ulbricht C, Basch E, Ulbricht C, et al. Wild yam (Dioscoreaceae). J Herb Pharmacother 2003;3(4):77-91. View Abstract
Wu WH, Liu LY, Chung CJ, et al. Estrogenic effect of yam ingestion in healthy postmenopausal women. J Am Coll Nutr 2005;24(4):235-243. View Abstract
Copyright © 2013 Natural Standard (www.naturalstandard.com)
The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.
March 22, 2017